[PATCH v7 09/25] ACPI / APEI: Generalise the estatus queue's notify code

James Morse
2018-12-03T18:09:22Z

Refactor the estatus queue's pool notification routine from
NOTIFY_NMI's handlers. This will allow another notification
method to use the estatus queue without duplicating this code.

This patch adds rcu_read_lock()/rcu_read_unlock() around the list
list_for_each_entry_rcu() walker. These aren't strictly necessary as
the whole nmi_enter/nmi_exit() window is a spooky RCU read-side
critical section.

_in_nmi_notify_one() is separate from the rcu-list walker for a later
caller that doesn't need to walk a list.

Signed-off-by: James Morse <james.morse@arm.com>
Reviewed-by: Punit Agrawal <punit.agrawal@arm.com>
Tested-by: Tyler Baicar <tbaicar@codeaurora.org>

---
Changes since v6:
* Removed pool grow/remove code as this is no longer necessary.

Changes since v3:
* Removed duplicate or redundant paragraphs in commit message.
* Fixed the style of a zero check.
Changes since v1:
* Tidied up _in_nmi_notify_one().
---
drivers/acpi/apei/ghes.c | 63 ++++++++++++++++++++++++++--------------
1 file changed, 41 insertions(+), 22 deletions(-)

diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
index d06456e60318..366dbdd41ef3 100644
--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c
@@ -907,37 +907,56 @@ static void __process_error(struct ghes *ghes)
#endif
}

-static int ghes_notify_nmi(unsigned int cmd, struct pt_regs *regs)
+static int _in_nmi_notify_one(struct ghes *ghes)
{
u64 buf_paddr;
- struct ghes *ghes;
- int sev, ret = NMI_DONE;
+ int sev;

- if (!atomic_add_unless(&ghes_in_nmi, 1, 1))
- return ret;
+ if (ghes_read_estatus(ghes, &buf_paddr)) {
+ ghes_clear_estatus(ghes, buf_paddr);
+ return -ENOENT;
+ }

- list_for_each_entry_rcu(ghes, &ghes_nmi, list) {
- if (ghes_read_estatus(ghes, &buf_paddr)) {
- ghes_clear_estatus(ghes, buf_paddr);
- continue;
- } else {
- ret = NMI_HANDLED;
- }
+ sev = ghes_severity(ghes->estatus->error_severity);
+ if (sev >= GHES_SEV_PANIC) {
+ ghes_print_queued_estatus();
+ __ghes_panic(ghes);
+ }

- sev = ghes_severity(ghes->estatus->error_severity);
- if (sev >= GHES_SEV_PANIC) {
- ghes_print_queued_estatus();
- __ghes_panic(ghes);
- }
+ __process_error(ghes);
+ ghes_clear_estatus(ghes, buf_paddr);

- __process_error(ghes);
- ghes_clear_estatus(ghes, buf_paddr);
+ return 0;
+}
+
+static int ghes_estatus_queue_notified(struct list_head *rcu_list)
+{
+ int ret = -ENOENT;
+ struct ghes *ghes;
+
+ rcu_read_lock();
+ list_for_each_entry_rcu(ghes, rcu_list, list) {
+ if (!_in_nmi_notify_one(ghes))
+ ret = 0;
}
+ rcu_read_unlock();

-#ifdef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
- if (ret == NMI_HANDLED)
+ if (IS_ENABLED(CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG) && !ret)
irq_work_queue(&ghes_proc_irq_work);
-#endif
+
+ return ret;
+}
+
+static int ghes_notify_nmi(unsigned int cmd, struct pt_regs *regs)
+{
+ int ret = NMI_DONE;
+
+ if (!atomic_add_unless(&ghes_in_nmi, 1, 1))
+ return ret;
+
+ if (!ghes_estatus_queue_notified(&ghes_nmi))
+ ret = NMI_HANDLED;
+
atomic_dec(&ghes_in_nmi);
return ret;
}
--
2.19.2